This invention relates to magnetic recording media, and more particularly, to improvements in magnetic recording media having a magnetic layer of the continuous thin film type.
Among magnetic recording media for use in video, audio and other applications, active research and development work has been made on magnetic recording media, usually magnetic tapes having a magnetic layer in the form of a continuous thin film because of the compactness of a roll of tape.
The preferred magnetic layers for such continuous film type media are deposited films of Co, Co-Ni, Co-O, Co-Ni-O and similar systems formed by the so-called oblique incidence evaporation process in which cobalt and optional elements are evaporated and directed at a given angle with respect to the normal to the substrate because such evaporated films exhibit superior characteristics. The evaporated magnetic layers, however, have many disadvantages including high dynamic friction, low film strength, rough head contact, and low runnability (that is, the durability of tape which travels in frictional contact with rigid members in a video equipment) resulting in reduced output after repeated travels. In the case of video application, the evaporated magnetic layers exhibit a short life time when operated in the still mode (to be simply referred to as "still life", hereinafter). In addition, there occur many dropouts in such layers.
Under these circumstances, a variety of topcoats have heretofore been proposed which cover obliquely evaporated magnetic layers. Exemplary of the topcoat are a variety of plasma-polymerized films as disclosed in Japanese Patent Application Kokai Nos. 58-194131, 57-135442, 57-135443, 57-198542 and 58-102330, and a variety of vapor deposited and coated films as disclosed in Japanese Patent Application Kokai Nos. 53-88704 and 53-93533 and Japanese Patent Aoplication Nos. 57-234816 and 57-234817. However, these topcoats formed by the conventional methods are not fully satisfactory, exhibiting insufficient corrosion resistance and low runnability at a low temperature.